Trellis systems are commonly used in agriculture to support vines for production of wine grapes, table grapes, raisins or other vine-derived fruit. Trellis systems typically utilize a row of vertical supports or posts, with one ore more trellis wires extending along the row of posts at selected heights to provide support for vines. Cross arm structures may be used in connection with the vertical stakes to provide a variety of trellis configurations.
It is often desirable to re-position trellis wires as vines grow and develop. The trellis wires are usually held onto a stake, cross-arm or other support by bendable wire clips that are physically bent around the trellis wire and the support to hold the trellis wires thereon. In order to move or re-position the trellis wires, the wire clips must be un-bent or cut to unfasten the trellis wire from the support. The wire clips generally cannot be used again, and once the trellis wire is re-positioned with respect to the support, the trellis wire must be fastened in place with new wire clips that are again bent to hold the trellis wire in place. The re-positioning of trellis wires throughout an entire vineyard is a time consuming, labor-intensive operation.
One of the most common trellis systems used in commercial grape production is the single vertical shoot propagation or “VSP” configuration wherein all of the trellis wires are positioned within the plane defined by a row of vertical posts or stakes. The cordons of the vines are trained along the wires within the plane defined by the stakes, and the vine fruit is located generally along the plane. This arrangement is relatively easy to install and is amenable to machine harvesting techniques.
Worldwide interest in quality wines has increased greatly during recent years, and large amounts of acreage have accordingly been committed to growing wine grapes. The majority of this acreage has been set up using single VSP trellising. It has become increasingly clear in the wine and grape growing industries, however, that the single VSP trellis configuration is non-optimal for quality wine grapes. The single VSP trellis generally does not allow sunlight to reach the cordon wood, which hinders lignification of vine shoots trained along the trellis wires and reduces grape quality. The single VSP configuration also does not provide an effective shade canopy for fruit and results in sun-damage and reduced fruit quality. Further, since the vines within a single VSP trellis system are all located within a single vertical plane, the fruit suspended within the plane are held in close proximity to leaves and tend to be more susceptible to mold and moisture damage, which further reduces fruit quality.
As a result of the aforementioned drawbacks in single VSP trellis systems, new wine grape acreage, in many cases, is being developed with “dual VSP” trellising such as “V”-shaped trellises and the quadralateral Geneva double curtain or “GDC” trellis configuration. Additionally, wine grape acreage that was previously developed with single VSP trellising is being re-configured or retrofitted for dual VSP trellising. These dual VSP arrangements provide dual planes of trained cordons defining a leaf canopy that allows sunlight to penetrate into the center of the canopy to reach the cordon wood. The GDC or quadralateral system has become increasingly disfavored in that the GDC vine canopy hangs down over the fruiting zone, and while opening the interior vine main trunk to sunlight, has caused significant problems with crop mildew, uneven ripening, and requires longer hang time for ripening. This causes harvests to extend in to late fall and wet conditions and results in more difficult and expensive harvests and the need for more sulfur and anti-fungal spraying.
The installation of dual VSP trellising in vineyards is more complex and expensive than that of conventional single VSP trellising. In addition to the simple vertical posts required for single VSP trellising, at least two additional risers are required in association with each post to define dual planes for vine propagation. Additionally, one or more cross arms are typically required on the vertical stake to support the risers. The available GDC and “V”-shaped trellis systems typically require the bending of structural elements to define the dual VSP configuration, and welded components can be required. In some instances, welding operations in the field are used, resulting in further expense and difficulty.
There are numerous drawbacks associated with installation of dual VSP trellising in the above manner. The fabrication of bent and welded components adds substantial expense to vineyard establishment or retrofitting of existing vineyards. Bent components and components that have been previously welded together are bulky and do not stack together well, and the shipping costs associated with moving large numbers of such components into the field can be substantial. The bending and welding of metal components typically results in damage to exterior finish on the components and promotes rust and reduces component lifetime. Further, the assembly of the currently available dual VSP trellis systems is complex and that lends itself to frequent errors in trellis assembly. Personnel in the field that are involved in vineyard trellis assembly are typically compensated on a piece-work basis and are unmotivated to correct errors that arise in the relatively complex assembly of available dual VSP trellis systems.
There is accordingly a need for trellising systems and methods that allow quick and easy re-positioning of trellis wires with re-usable wire clips, which facilitate the installation of dual VSP trellising and the retrofitting of single VSP trellising to dual VSP trellising, which do not require any bending or welding operations for fabrication or installation of trellis components, and which provides quick, easy, error-free trellis assembly. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in the background art.